386 PROCEEDINGS OF THE ACADEMY OF 



there are usually three, or occasionally four, irregular elongated pieces, similar 

 to the upper of the anal series. Sometimes the middle one of these three 

 pieces extends down between the others, so as to rest upon a short, truncated, 

 upper end of the first interradial piece. (Other parts unknown.) 



Height from base to top of vault, 0-47 inch ; do. to arms, 037 inch ; breadth 

 across, from side to side, between the interradial 0-66 inch. 



Locality and position. Same as last. 



Actinocrinus speciosus. Body large, below the arms obconical, longer than 

 wide, composed of convex, ornately co3tate plates, which are joined by more or 

 less excavated sutures. Base of moderate size, cup-shaped, nearly as wide 

 again as high, truncate below, and expanding rather rapidly upward, composed 

 of regular subequal hexagonal plates, with broadly and deeply grooved sutures. 

 Columnar facet rather large, or nearly equaling one- half the breadth of the 

 base, flat, marked by obscure radiating strife, and provided with a very small 

 continuous rim ; perforated by a round central opening about one-third the 

 diameter of the column at its junction with the body. First radial plates large, 

 longer than wide, three hexagonal, and two heptagonal, generally widest a 

 little above the middle. Second radials considerably smaller than the first, 

 about as wide as long, and apparently all hexagonal. Third radials a little 

 smaller than the second, wider than long, heptagonal, (and octagonal ?) each 

 supporting on its superior sloping sides two smaller heptagonal or octagonal 

 secondary radials, which appear to have each supported two brachial pieces ; 

 resting upon and between the two secondary radials, there is a small hexagonal 

 interbrachial [piece, which appears to have supported two others on its upper 

 sloping sides. 



The first anal plate, which is nearly as large as the first radials, is heptagonal, 

 longer than wide, and supports in the first range three much smaller pieces, 

 the middle one of which, is pentagonal, and the others hexagonal; above these 

 in the next range, there are four, and in the third, apparently three pieces, 

 which is as far as they can be traced in the specimen examined. 



The first interradial plates are slightly larger than the second radials, hexa- 

 gonal, and each surmounted by two smaller pieces ; above these there are, 

 apparently, about three other ranges of two small pieces each. 



The surface of the plates is neatly ornamented by narrow, sharply elevated 

 ribs, about four to six of which radiate from the central region of each first 

 radial plate to each of its sides, excepting below the middle, where there are 

 usually about eight to ten. The costae on the other plates are less numerous 

 in proportion to the size of each, and like those on the first radials, extend to 

 the sides, those crossing any one side being all arranged parallel to each other 

 so as to form with those on the adjacent plates a series of concentric equila- 

 teral triangles. Sometimes these costas are irregularly interrupted, or more or 

 less notched, especially on the upper plates ; and on some of the upper inter- 

 radial pieces they show a tendency to become irregularly broken up into little 

 spine-like projections. 



Locality and position. Three miles west of Burlington, Iowa. Burlington 

 Limestone of the subcarboniferous series. 



Actixoceinus scilutds. Body [rather under medium size, unsymmetrically 

 urn-shaped, the summit being moderately convex, and the calyx below the 

 arms obconical, with a truncated base ; expanding regularly with straight 

 sides from the base to the third radials, above which the secondary radial, and 

 first brachial pieces extend out horizontally, leaving excavated interradial 

 spaces between the clusters of arms ; sutures close fitting. Base of moderate 

 size, more than twice as wide as high, truncated, and distinctly concave below, 

 where it is as wide as at the summit ; margin so deeply notched at the sutures 

 as to present a distinctly trilobate appearance as seen from below ; columnar 

 facet rounded, aboxit one-third as wide as the base, and provided with a mi- 

 nute central perforation. First radial pieces a little wider than long, two of 

 them heptagonal, and three hexagonal, widening upwards from the base to 



[Sept. 



